This Budapest bar allows drinkers to leave their mark on the walls, floor, and even ceiling.

The remains of an entire Roman city can be explored in this interactive museum.

Venice's island of the dead.

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

The "dragon babies" of southeastern Europe.

This massive subterranean fissure is known as the "underground Grand Canyon."

Where the lovelorn find a home for their sentimental keepsakes.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

Two bulls enter. One leaves a champion—but neither loses its life.

Bridge that died in war and was resurected.

A musical instrument played by the sea.

An ethereal glowing blue ocean cave in Croatia.